Design, fabrication, and characterization of third-order dispersion mirrors for femtosecond lasers

The residual third-order dispersion (TOD) in ultrafast laser systems must be compensated. We developed an initial design method for a low-oscillation TOD mirror (TODM). The optimized TODM provided a TOD of -5000 fs³ with oscillations less than ±50 fs³ in a wavelength range of 890-960 nm. To meet the requirements of an all-fiber femtosecond laser system, we simulated the application of the TODM in an ultrafast laser system to compensate for a positive TOD of +2.5 × 10⁵ fs³. Sidelobe pulse oscillations were significantly suppressed after TODM compression, thereby improving pulse quality. Moreover, the laser-induced damage threshold of the TODM was measured to be approximately 0.20 J/cm² under irradiation with 16 fs laser pulses with a spectral bandwidth of 200 nm centered at 920 nm. The initial damage locations on the mirror were successfully explained using multiwavelength electric field analysis. This study provides a basis for the subsequent design of TODMs and the study of the femtosecond damage of dispersion mirrors.